Answer:
The Incas were magnificent engineers. They built a system of roads and bridges across the roughest terrains of the Andes. Through their system of collective labor and the most advanced centralized economy, the Incas were able to secure unlimited manual labor.They built more than 14,000 miles of paved road that connected Cuzco, the capital, to all corners of the empire.
Bridges were built everywhere in the empire. Their suspension bridges were built using natural fibers. Indigenous people still use the same technique in remote areas in the Andes. Communication was very important to maintain Inca policy. Considering that the Incas did not know the use of the wheel and that their only transportation was llamas or alpacas, it is astonishing that they were able to control such large territory and maintain peace until they were invaded by the Spanish conquistadors.